Junos
Junos

ISIS Routes Priority

a week ago

Hi guys,

I'm preparing JNCIS-SP and refreshing ISIS concetps I noticed that exists a priority in ISIS to change the behaviour of how to treat the routes.

I have never used this statement in order to prefer one route or another. (Attached image)

Someone used before and think if is useful?

IS-IS_priority.png

As far as I know most powerful is to use route preference or secondary route preference as tiebreak.

Many thanks, 

 

2 REPLIES 2
Junos

Re: ISIS Routes Priority

a week ago

Hello,

The HighPriority field is related to route installation in the FIB. Please check out this link

https://www.juniper.net/documentation/en_US/junos/topics/task/configuration/configuring-priority-hig...

It is useful to prioritize installation of certain important prefixes, like DNS server IPs, company portal, etc to make sure Your customers can at least reach Your company portal to read messages about outages should they happen.

HTH

Thx

Alex

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Junos

Re: ISIS Routes Priority

Sunday

Hi Alfredo,

 

This "high" priority is not related with route prefrence. Its related with route installattion order on the local router.

 

In case of network convergence low priority prefixes are installed only after the high priority prefixes in the routing table. These priorities can be applied via an import policy. Routes that are not explicitly assigned a priority are treated as medium priority.

 

If you want to see this in action you can perfrom routing restart or anything else that you would trigger network convergance. It won't have any imact in steady state. 


Thanks
Vishal